Natural selection and demography as causes of molecular non-randomness
Natural selection and demography as causes of molecular non-randomness
Chapter 7, “Natural selection and demography as causes of molecular non-randomness,” outlines the predictable molecular evolutionary patterns that arise when the Neutral Theory has its assumptions violated. It summarizes predictions about genetic variation, the shape of genealogies, and the accumulation of divergence between lineages when natural selection and non-standard demographic scenarios occur in populations. This chapter provides an overview of the general, qualitative impacts on molecular population genetic data by positive selection, purifying selection, and balancing selection, as well as by demographic population growth, contraction, and subdivision. It covers the concepts of selective sweeps, genetic hitchhiking, and background selection, placed in a heuristic context of skews in polymorphism, genealogies, the site frequency spectrum, and distinct metrics of divergence. This chapter also summarizes the consequences of genetic linkage to sex chromosomes and plastid genomes. This overview builds up intuition about selection, demography, and genome organization as important molecular population genetic factors that motivate further analysis with quantitative tests of neutrality.
Keywords: natural selection, positive selection, balancing selection, purifying selection, genetic hitchhiking, background selection, population expansion, population contraction, population structure, genome structure
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